What happens if you remove the PCV inlet from the carb and plug that port? Do you have a vacuum cap large enough to do that? If not, you can use a short length of the right size hose and thread a screw into the end of it.

If that does the trick, all I can think of doing is trying to find the right (different) PCV valve. This is assuming that everything else is now correct.

Shawn

Edit: I still don't like your PCV configuration but I'm grabbing at straws here. Does your spacer have a port for a PCV inlet? If it were mine, and whether it ran well as is or not, I'd mount my PCV inlet on the spacer and move it to the front of the carb and either plug the inlet at the back of the carb or use it for the power brakes.

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